WEEK 3: ELECTRICAL 03.05.2011-06.05.2011
The two weeks holiday was good because it gave me time to give my brain a rest, gave me time to revise over my notes and also get some work experience.
TUESDAY 3rd MAY 2011
First week back from the holidays, we started on a new practical work booklet called Starter motor bench testing and repair. We learnt different areas of the starter motor. These different areas consisted of understanding what to do with each component in the starter motor, testing those components then writing a report on my findings. By testing the components, it helped me to get a better understanding of the purpose of each component. For example, doing a visual inspection and checking for signs of overheating, burning, physical damage of insulation of coil windings and poling are important to do because of safety reasons so the starter motor can function properly. The starter motor that I tested was not working properly. The pinion gear wasn’t engaging into the fly wheel which meant I had to pull it apart and find out what was wrong. The reason why the pinion gear wasn’t engaging was due to the short circuit inside the starter motor from the field windings. In conclusion, our starter motor worked but it wasn’t safe due to some of our components tested right and some didn’t therefore the starter motor I tested wasn’t up to manufacturers specifications and as a result is a fail starter motor.
WEDNESDAY 4th MAY 2011
Today in class, we carried on with starter motor’s but on car testing. In the first half of the lesson, we got taught how to carry out tests on the components of the starter motor to get us ready for an assessment where we would have to carry out the tests ourselves. For some of the tests I done, I had to repeat them a few times so I could fully understand and remember the steps of these tests. In the second half of the lesson, I did an assessment on starter motor’s to see if I understood how to test each component. I did my assessment on my own car and had to do certain tests to find out if my understanding with starter motors was clear. There were certain checks that I had to do which first was the visual and safety check followed by finding out the starter voltage drop for the starter circuit. We had to find out the specifications that our volt drop had to be under and all of our tests were under that certain amount. This indicated that all my tests were correct. In summary, my condition of the starter motor is a pass. There were no problems and all the components I tested matched the manufacturer’s specifications. This also presented that my starter motor condition was 100% safe.
Due to a gas leak occurring in one of the class rooms upstairs, we had to evacuate the building stopping our lesson and interfering with my learning.
FRIDAY 6th MAY 2011
Today we learnt about Relays. Relays use a low amperage circuit to switch a higher amperage circuit. I had to construct up a circuit using a relay on the circuit board so the switching circuit of the relay will turn on one of the bulbs, and the control circuit of the relay will be controlled by the switch. There were several tests I did to understand how the relay functioned. My understanding with relays was slow but as I went over and over my work it help me understand it more clearly. The relay I used had 5 pins having printed a number of the terminal on the relay for its purpose. The pin designations are as followed 86 – positive side of control circuit (RED), 85 – negative side of control circuit (BLACK), 30 - battery supplies for switched circuit (YELLOW), 87a – normally closed switched circuit(BLUE), 87 – other switch circuit(YELLOW). Inside a relay there are two pathways for voltage to flow through, The controlled circuit and the switching circuit and how this works is when low amps in the control circuit creates magnetism to move the switch circuit points to the other position turning off one pathway of voltage and switching on another contact therefore allows you to turn on a higher amperage device. For example: When you switch your headlights from low beam to high beam a relay is used to switch from low to high beam.
